Added section 2.6.

Signed-off-by: bert <[email protected]>

Author: bert

2.6_auto_router.md

@@ -0,0 +1,76 @@
+# Auto Router
+
+## How do I make the most of the auto router?
+
+1.  Turn off visibility of any layers you don't want the router using.
+2.  Turn off via visibility if you don't want it to introduce any new
+    vias.
+3.  Use only plain rectangles for power/ground planes that you want the
+    router to use. (Use the rectangle tool rather than the polygon tool!)
+4.  Make at least one connection from any plane you want the router to
+    use to the net you want it to connect to.
+5.  Draw continuous lines on all routing layers to outline keep-out zones.
+6.  Use routing styles in the netlist to have per-net routing styles.
+7.  Set the current routing style for any nets not having a defined
+    route style in the netlist.
+8.  Disable any nets that you don't want the autorouter to route – 
+    double-click them in the netlist window to add/remove the “*”.
+9.  Create a fresh rat's nest. (press the <b>O</b> key)
+10. Select Show autorouter trials in the Settings menu if you want to
+    watch what's happening.
+11. Choose Auto-route all rats in the Connects menu.
+
+Note on disabled nets: If you will be manually routing these later not
+using planes, it is usually better to let the autorouter route them then
+rip them up yourself afterwards.
+If you plan to use a ground/power plane manually, consider making it
+from one or more pure rectangles and letting the autorouter have a go at
+it.
+
+If you really want to muck with the router because you have a special
+design, e.g. all through-hole components you can mess with layer
+directional costs by editing the autoroute.c source file and changing
+the directional costs in lines 929-940 and try again.
+Even more mucking about with costs is possible in lines 4540-4569, but
+it's probably not such a good idea unless you really just want to
+experiment.
+
+## How do I force the autorouter to only put traces on a particular layer?
+
+Just unselect the layers you don’t want (usually green and blue) by
+clicking on the name of the layer, then press autoroute.
+
+## How do I make autorouter leave particular nets alone?
+
+Open up the netlist window.
+It has options for including or excluding nets from the ratlist.
+If you use the GTK-HID double-click a route to disable it.
+Make sure, only the nets you want are enabled.
+Optimize the rats with key <b>O</b>.
+Do Auto-route all rats.
+
+## How do I force the autorouter to route only within my pcb outline?
+
+You can have the autorouter work only within a given area by drawing a
+copper polygon conforming to your board’s boundary and placing it in
+each layer you’re trying to autoroute.
+You can also use this trick to autoroute only with small areas.
+Of course, if you accidentally have a net touching the polygon, all
+routes will get shorted to that net.
+
+## How do I route power and ground planes with the autorouter?
+
+Connect the polygon that will become your power planes to a net and the
+autorouter will figure it all out.
+You may need some trick polygon clearances to get power routing and
+routing within a board outline.
+
+## The layout produced by the autorouter is inefficient!
+
+This is a technological limitation of the current auto router.
+It is gridless and uses geometric rectangles only.
+
+## The layout produced by the autorouter is ugly!
+
+Have you tried the various clean-up tools under
+<b><i>Connects → Optimize routed tracks</i></b> ?